Cartesian forms of $e^{i\theta}$, $3e^{i\pi/4}$, $\frac12 e^{i\pi}$, $2e^{2i\pi/3}$ and $e^{-3i\pi/4}$

Write the following complex numbers in cartesian form

\[ e ^ { i \theta } , \qquad 3 e ^ { i \pi / 4 } , \qquad { \frac { 1 } { 2 } } e ^ { i \pi } , \qquad 2 e ^ { 2 i \pi / 3 } , \qquad e ^ { - 3 i \pi / 4 } . \]